Devices to evaporate volatile substances in a liquid state are well known that consist of a wick of which one end is in contact with a volatile substance in a bottle, such that the substance rises by capillarity through the wick, which is made of a porous material, until this becomes totally impregnated.
Conventionally, these devices include heating devices, such as PTC electrical resistances, aimed at heating the upper portion of the wick that facilitates evaporation of the substance that dissipates to the exterior of the device in the form of vapor.
Some of these pieces of equipment are equipped with devices that permit the degree of evaporation of the product to be controlled, which are generally based on modifying the intensity of heating the wick. The need to control the degree of evaporation tends to complicate the design and manufacture of the device since several interconnecting parts are required, making the manufacturing process more expensive, which is a key factor in these products since the low production costs are the key to their profitability.
Some known devices of this kind use heating elements with a toroidal configuration such that one end of the wick is lodged in the central orifice, permitting uniform heating of the whole perimeter of the wick in the area of influence of the heating element. Although this toroidal shape of the heating element is effective from an operative perspective, the device as a whole increases in width and, therefore, size and this is undesirable from manufacturing and sales perspectives.
Some examples of this type of device can be found in the patents U.S. Pat. No. 4,739,928, EP-1.270.022, U.S. Pat. No. 6,659,301.